The present application relates generally to determining the target thermal conditioning value to control a rechargeable energy storage system (RESS), and more particularly to systems and methods determining the target thermal conditioning value using thermal power and heat generation values.
Automotive technology is rapidly expanding in the area of finding alternatives to using gasoline as the primary source of energy in vehicle propulsion systems. Many of these advances utilize either a hybrid mechanical-electrical system that recaptures some of the mechanical energy from the combustion engine as stored electrical energy, or a fully-electric propulsion system, which eliminates the need for an internal combustion engine entirely. With these advancements, the storage and management of electrical energy in vehicles has become of particular importance.
Hybrid and electric vehicles provide an alternative to conventional means of vehicular motive power by either supplementing (in the case of hybrids) or completely replacing (in the case of electric vehicles) the internal combustion engine (ICE). The hybrid variant of such alternative vehicle is known as an extended range electric vehicle (EREV). In one embodiment of the EREV, primary electric drive is achieved with a RESS that acts as a direct current (DC) voltage source to a motor, generator or transmission that in turn can be used to provide the energy needed to rotate one or more of the vehicle's wheels. Once the electrical charge from the RESS has been depleted, backup power may come from an ICE to provide auxiliary onboard electrical energy generation. One form of battery that appears to be particularly promising for RESS vehicular applications is known as a lithium-ion battery.
Because the RESS forms a significant part of the vehicle's propulsion system, it is important to monitor RESS parameters to ensure proper vehicular performance. Examples of such parameters include temperature, voltage, state of charge and so forth. Of these parameters, the temperature of the RESS is particularly important for the RESS and its energy consumption. The RESS must be kept within a temperature range so that it can effectively operate, i.e., its charge capacity and cycle life can be optimized. An optimal system needs to consider temperature for both heating and cooling. In order to drive the temperature within an optimal range, the required thermal power has to be quantified. Once the thermal power is determined, energy consumption can be changed to accommodate a heating or cooling event.
While temperature may be readily measured, it is difficult to relate such temperature to a way to drive one or more high voltage devices for RESS heating or cooling. This in turn hampers efficient operation of the RESS, as well as the ability to operate the RESS in a manner that will avoid temperature-related component failure.
Conventional systems and methods of determining thermal conditioning involve estimates, and tend to not be exact enough to determine how much thermal conditioning is needed to drive the battery for RESS heating and/or cooling. A more precise amount of thermal conditioning is needed in order to determine how much to drive high voltage devices for RESS heating or cooling.